A system for dental prostheses commonly used today comprises a more or less cylindrical fixture which is inserted into a bore-hole drilled into the uncovered jawbone. The system further comprises a conical abutment or pillar, intended to carry the prosthesis, which is to be attached to the fixture, thus bridging the layer of soft tissue covering the jawbone. The abutment is complementary to a conical bore in the top of the fixture. The abutment is provided in several standard lengths in order to allow the correct choice of abutment in dependence of the thickness of the soft tissue around the implant site after implantation.
The choice of the correct abutment is very important inter alia for esthetic reasons. This choice may however be time-consuming and may also be troublesome for the patient. There thus is a need for a tool which facilitates the choice of abutment and which is simple to use and to read in the environment of the oral cavity.
It may also be difficult to chose the correct fixture which is to fit into the hole drilled into the bone. It is important that the fixture is flush with the uncovered bone tissue or slightly below the edge of the bore-hole.
Generally, when implants are fitted into bone tissue, different kinds of metallic surgical tools are used to prepare the site in the tissue where the implant is to be located. These tools normally are made of carbon steel (normally in disposable tools) or surgical grade stainless steel or titanium or titanium alloys (normally in non-disposable tools).
In some cases it may be advantageous if at least the surface of the tools are covered with a material which is more biocompatible than the material in the tool even if the tool is not to remain in the bone tissue for a long period of time.
If the tool is not of an inert material as regards the chemical environment prevalent in bone tissue and blood, some slight contaminations may affect the sides of the bore hole. These contaminants might possibly affect the so-called osseointegration process which seems to be very important in connection with bone implants and which seems to be sensitive in respect of contaminants.
Another prerequisite for a good osseointegration is a good, stable fit between bone tissue and implants, the osseointegration being dependent on a close contact between bone tissue and implant surface. When a bore-hole for an implant has been drilled, it therefore is important that the length of the bore-hole corresponds as closely as possible to the length of the implant chosen.
If the bore-hole in the jaw-bone should happen to be too shallow for the implant which has been deemed to be suitable in a specific location in the oral cavity, it is important to be able to ascertain this in advance, because of the trauma to the bone tissue that might be the consequence of the implant first being screwed into the bore-hole and then being unscrewed again. If it is vital that the implant chosen actually is used in this specific location, the threads in the bore also might be damaged by the necessary, additional drilling procedure.